The present invention relates to loudspeaker cabinets composed of a moldable wood material and a method for making the same. In particular, the present invention relates to loudspeaker cabinets composed of a compression molded cellulose (CMC) material resulting in a cabinet for loudspeakers with improved acoustic and physical properties.
The quality of sound created by a loudspeaker is significantly influenced by the shape of the cabinet in which it is mounted and by the acoustic properties of the material from which the cabinet is made.
Loudspeaker cabinets are traditionally constructed of various types of wood or fabricated wood materials such as particle-board, press board, plywood, and fiberboard that are available only in sheet form. Cabinets fabricated from sheets of material possess angular junctions and flat internal surfaces that degrade the accuracy of the sound generated by the loudspeaker. Flat internal cabinet surfaces reflect sound waves in a regular pattern that interfere with the waves emanating from the loudspeaker. This interference creates standing wave cancellation resulting in distortion and loss of loudspeaker efficiency. The quality of reproduced sound from traditional xe2x80x9cboxxe2x80x9d shaped loudspeaker cabinets is inferior to the quality of reproduced sound from loudspeaker cabinets incorporating curved internal surfaces. Curved internal cabinet surfaces reflect sound waves randomly thereby minimizing standing wave cancellation and distortion and enhancing efficiency.
Additionally, the leakage of air at the connection points of flat panels adversely affects the loudspeaker""s overall performance. Molded cabinet construction eliminates joints thereby ensuring a leak-proof cabinet.
Traditional cabinet materials are available only in fixed densities as they are generally intended for architectural and/or structural applications. The densities are not always ideal for acoustic applications since the rate of decay of the sound energy in the material directly affects the quality of the sound produced by the loudspeaker incorporated into cabinets composed of these materials. In contrast, the density of compression molded cellulose (CMC), the present invention, can be controlled and modified by formulation and process variations to conform to specific acoustic criteria. This flexibility greatly enhances the quality of the sound from the loudspeaker mounted in the CMC cabinet.
There is a need in the industry for loudspeaker cabinets, and a material and process for making the same, with improved acoustic and physical properties. There is also a need in the industry, especially the automotive, marine, and other applications, for a loudspeaker cabinet and material with a greater resistance to water, weather, and abrasion damage. There is also a need in the industry for a moldable material with improved physical properties such as abrasion and water resistance for use in non-loudspeaker applications.
Currently available loudspeaker cabinets are also limited in the designs available with regard to shape and surface detail due to the materials employed. Plastic or non-cellulose based materials may be available, but are not readily capable of accepting paint or other decorative treatments, may be difficult to work with, and the costs of production may be prohibitively high.
In many applications, loudspeaker performance is enchanced if the cabinet can be made airtight. Cabinet construction using traditional materials with angular joints makes airtight cabinet construction nearly impossible. There is a need in the industry to provide cabinets that are airtight.
There is also a need in the industry to provide loudspeaker cabinets with various densities to match the requirements of the loudspeaker. There is also a need in the industry to be able to manufacture cabinets with the above advantages from readily available materials with predictable costs. There is also a need in the industry to provide loudspeaker cabinets with an increased service life which are not susceptible to rot or other types of decay or degradation. There is also a need in the industry for a material which is capable of being manipulated (cut, drilled, threaded, sanded, etc.) easily with standard tools and techniques. There is also a need in the industry to provide loudspeaker cabinets which are not only impermeable to water and other liquids, but also to gases and other fumes which may be harmful to the loudspeaker components. There is also a need in the industry to provide loudspeaker cabinets not only with varying material densities, but also with controllable and variable wall thickness.
It is an object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets having improved acoustic properties.
It is another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets having improved physical properties.
It is a further object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets having unlimited design latitude with regard to shape and surface detail.
It is still another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets having high resistance to water and weather and abrasion damage.
It is yet another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets capable of accepting paint and or other decorative treatments.
It is still yet another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets having a lower per unit fabricated cost.
It is another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets having the ability to be produced by simple methods such as low-pressure compression molding using fabricated tooling.
It is another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets having few or no seams or joints ensuring an air-tight enclosure.
It is another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets of varying material densities to meet the specific requirements of various acoustic applications.
It is another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets from readily attainable materials with predictable costs.
It is another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets with long service life capability.
It is another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets with the capability of being manipulated with standard tools and techniques.
It is another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets that are impermeable to water and air.
It is another object of the present invention to provide a material and process with which to fabricate loudspeaker cabinets that are of controllable and uniform wall thickness.
Additional objects and advantages of the invention are set forth, in part, in the description which follows and, in part, will be apparent to one of ordinary skill in the art from the description and/or from the practice of the invention.
In response to the foregoing challenge, Applicants have developed an innovative, economical material and process yielding weatherproof cabinets of any shape, which have greater acoustic integrity and improved physical properties at a lower cost per unit. The material, compression molded cellulose (CMC) is a novel blend of wood fibers and other organic and inorganic fillers bonded within a matrix of thermoset resins.
In accordance with the present invention, a process for the mixing, extrusion, and compression molding of the CMC material has been developed which employs standard commercially available equipment in combination with specifically designed presses and molds. The equipment employed is inexpensive and simple to maintain and operate.
Molds developed for this process and material may be fabricated quickly at low cost and at the site of production of the loudspeaker cabinets. Cabinet designs with rounded forms are made possible using the material and process. The characteristics of the material in combination with the unique shape of each cabinet is designed to enhance the fidelity of the sound produced by the loudspeaker by reducing the sound-wave cancellation and distortion typically found in cabinets with flat surfaces. (See FIG. 6 and FIG. 7 for results of free air testing of an embodiment of the present invention, a typical 10xe2x80x3, 0.65 cu. ft. sub woofer cabinet).
In an embodiment of the present invention, a loudspeaker cabinet comprises at least one wall made of a compression molded cellulose material. The loudspeaker cabinet may comprise a face portion, a shell portion, and means to join the face portion to the shell portion, wherein the shell portion and/or the face portion is composed of a compression molded cellulose material. The loudspeaker cabinet may include a shell portion containing a recessed area to accommodate speaker terminal connections, and a face portion possessing a means to mount a loudspeaker to the face portion. The loudspeaker cabinet may possess a shell portion and a face portion with curved interior and exterior surfaces. The loudspeaker cabinet may also contain compression molded cellulose material that is of uniform density.
In an embodiment of the present invention the loudspeaker cabinet of compression molded cellulose material may comprise thermoset resins in the range of 25-85% and a catalyst in the range of 1-5%. In addition to the thermoset resins and the catalyst, the loudspeaker cabinet of compression molded cellulose material may be comprised of at least one of the following: milled glass fiber in the range of 1-10%; fine wood flour in the range of 1-20%; course wood flour in the range of 10-40%; glass beads in the range of 5-20%; fly ash in the range of 5-20%; colloidal silica in the range of 0.5-3%; fine grind calcium carbonate in the range of 5-20%; alumina trihydrate in the range of 5-20%; elastomeric particulate in the range of 2-15%; a foaming agent in the range of 1-3%; organic fibers in the range of 5-10%; and finely divided metallic material in the range of 20-50%.
The thermoset resins may be selected from, but not limited to, the group comprising polyester thermoset resins, unsaturated polyester thermoset resins, polyurethane thermoset resins, epoxy thermoset resins, and phenolic thermoset resins. The thermoset resin may be a blended unsaturated polyester thermoset resin, or any hybrid combination of thermoset resins. The fine wood flour may be mesh size 100-200, the course wood flour may be mesh size 10-50, the elastomeric particulate may be comprised of rubber and/or rubber tire regrind.
The catalyst may be, but is not limited to, Methyl Ethyl Ketone Peroxide and/or Methyl Ethyl Ketone Peroxide 9% free oxygen. The foaming agent may be 1,1-dimethylethyl hydrazine chloride and/or iron chloride. The organic fibers may be mesh size 10-60 and may be jute. The metallic material may be, but is not limited to, lead.and/or aluminum.
In an embodiment of the present invention, a loudspeaker cabinet may be comprised of a compression molded cellulose material, wherein the compression molded cellulose material comprises unsaturated polyester thermoset resins in the range of 90-99% and the catalyst Methyl Ethyl Ketone Peroxide 9% free oxygen in the range of 1-10%.
A method of manufacturing a loudspeaker cabinet of a compression molded cellulose material may comprise the steps of: blending dry compression molded cellulose ingredients in a first blender to form a blended dry compression molded cellulose mixture; mixing liquid compression molded cellulose ingredients, excluding a catalyst, in a first mixer to form a mixed liquid compression molded cellulose mixture; continuously combining the blended dry compression molded cellulose mixture and the mixed liquid compression molded cellulose mixture in a second mixer to form a high viscosity compression molded cellulose mixture; pumping the high viscosity compression molded cellulose mixture into a third mixer by means of a first pump while simultaneously introducing a catalyst into the high viscosity compression molded cellulose mixture by means of a second pump to form a catalyzed compression molded cellulose mixture; extruding the catalyzed compression molded cellulose mixture into at least one male or female mold of at least one of a male and female mold set; heating the catalyzed compression molded cellulose mixture upon introduction to the at least one male or female mold to 100-200 degrees F.; closing the at least one mold set to distribute the catalyzed compression molded cellulose mixture; compressing the at least one mold set to pressures of between 5-100 PSI; maintaining the pressure until the catalyzed compression molded cellulose mixture forms at least one cured compression molded cellulose part; opening the at least one mold set and removing the at least one cured compression molded cellulose part; removing flash from the at least one cured compression molded cellulose part; and bonding the at least one cured compression molded cellulose part using a compatible adhesive.
The dry compression molded cellulose ingredients may comprise at least one of milled glass fiber, fine wood flour, course wood flour, glass beads, fly ash, colloidal silica, calcium carbonate, alumina trihydrate, elastomeric particulate, organic fibers, or finely divided metallic material. The liquid compression molded cellulose ingredients may comprise thermoset resins and/or a foaming agent. The first blender may be a ribbon blender. The first mixer may be a high shear mixer of the batch or continuous type. The second mixer may be an auger mixer.
The high viscosity compression molded cellulose mixture may be formed in a temperature and/or vacuum controlled environment. The high viscosity compression molded cellulose mixture may be pumped into the third mixer at a rate of 7000-10000 centimeters per second. The third mixer may be a static mixer or a multi element static mixer. The first pump and the second pump may be positive displacement pumps, and the first pump may be functionally linked to the second pump.
The catalyzed compression molded cellulose mixture may be extruded into the at least one male or female mold by use of a metering extrusion head. The catalyzed compression molded cellulose mixture may heated by means of at least one heated mold surface and/or by means of at least one heater at the point of extrusion. The pressure may be maintained from between 5-20 minutes after addition of the catalyst.
In an embodiment of the present invention, a loudspeaker cabinet may be comprised of compression molded cellulose material, wherein the compression molded cellulose material comprises: thermoset resin in the range of 71-83%; coarse wood in the range of 10-16%; fine wood in the range of 1-3%; glass bead in the range of 4-8%; silica in the range of 0.1-2%; and catalyst in the range of 1-3%. The thermoset resin may be an unsaturated polyester thermoset resin. The course wood may 20 mesh pine wood flour. The fine wood may 100 mesh pine wood. The silica may be AeroSil. The catalyst may be Methyl Ethyl Ketone Peroxide 9% free oxygen.
In an embodiment of the present invention, the compression molded cellulose material may comprise thermoset resins in the range of 25-85% and a catalyst in the range of 1-5%. In addition, the compression molded cellulose material may comprise at least one of the following: milled glass fiber in the range of 1-10%; fine wood flour in the range of 1-20%; course wood flour in the range of 10-40%; glass beads in the range of 5-20%; fly ash in the range of 5-20%; colloidal silica in the range of 0.5-3%; fine grind calcium carbonate in the range of 5-20%; alumina trihydrate in the range of 5-20%; elastomeric particulate in the range of 2-15%; a foaming agent in the range of 1-3%; organic fibers in the range of 5-10%; and finely divided metallic material in the range of 20-50%.
The thermoset resins may be selected from, but not limited to, the group comprising polyester thermoset resins, unsaturated polyester thermoset resins, polyurethane thermoset resins, epoxy thermoset resins, and phenolic thermoset resins. The thermoset resin may be a blended unsaturated polyester thermoset resin, or any hybrid combination of thermoset resins. The fine wood flour may be mesh size 100-200, the course wood flour may be mesh size 10-50, the elastomeric particulate may be comprised of rubber and/or rubber tire regrind.
The catalyst may be, but is not limited to, Methyl Ethyl Ketone Peroxide and/or Methyl Ethyl Ketone Peroxide 9% free oxygen. The foaming agent may be 1,1-dimethylethyl hydrazine chloride and/or iron chloride. The organic fibers may be mesh size 10-60 and may be jute. The metallic material may be, but is not limited to, lead.and/or aluminum.
All the above elements work together to yield a loudspeaker cabinet with excellent sound quality at a practical cost. The novel characteristics of the CMC material permit fabrication of the cabinets in various shapes, sizes and densities in order to match the requirements of the loudspeaker. The process and tooling permit the cabinet to be fabricated for a lower cost than other available technologies.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only, and are not restrictive of the invention as claimed. The accompanying drawings, which are incorporated herein by reference, and which constitute a part of this specification, illustrate certain embodiments of the invention and together with the detailed description serve to explain the principles of the present invention.